Please have a look at the metalink note 601832.1. Hope this will help you help.
REMIT_ADVICE_DELIVERY_METHOD Column in the table IBY_EXTERNAL_PAYEES_ALL, can not be updated using any Public API. There is an API IBY_DISBURSEMENT_SETUP_PUB, which is closely used for updating this table. But there is no such Public API to update this field.